The accurate determination of the location of an object is of immense value. The Global Positioning System (GPS) maintained by the U.S. government allows accurate location determination based upon the simultaneous receipt of broadcast data signals from GPS satellites and the calculation of positional information based upon differences in arrival times of simultaneously-broadcast signals. While GPS position data is highly accurate, it requires reception of multiple satellite transmissions. These transmissions may not be accessible at al times and at all locations, and particularly in urban areas and indoors.
U.S. Pat. No. 6,799,047 to Bahl, et al, “Locating and Tracking a User in a Wireless Network through Environmentally Profiled Data” describes an alternate system that determines a location of a user receiver, and particularly within a building, by measuring the signal strength of fixed base stations of a wireless local area network in the building or comparable known physical environment. The signal strengths are measured and compared to a tabulation of signal strengths and locations. Thus use of the system is limited to the range of the particular set of base stations and the generally limited range of their broadcasts. Bahl does not address wide ranging field situations where a mobile device, such as a mobile phone or wireless enabled hand held device, is beyond the known base stations' environment.
It is accordingly a purpose of the present invention to provide a method and apparatus by which a mobile device is not limited by the particular operating range of a particular base station system for position determination. The present invention comprises a preferably mobile device to sense a variety of environmental parameters, such as radio signals, interference and signal parameters of a broad spectrum of other signal sources that may exist in the local environment. Unlike devices in the prior art, the present invention can utilize all available data that can be sensed by the receiver apparatus, thus allowing the local environment to be characterized for future reference for comparison purposes, but with a recognition that the environment is not static but subject to dynamic reconfiguration and alteration as a result of local conditions.